It is well accepted that hypothalamic control over the release of the anterior pituitary hormones is brought about by the release of peptidic releasing and inhibiting hormones into the hypophyseal portal vessels and five of these, namely thyrotropin-releasing hormone (TRH)l luteinizing hormone releasing-hormone (LHRH), growth hormone release inhibiting hormone (somatostatin, panhibin), corticotrophin-releasing factor (CRF), and growth hormone-releasing factor (GRF) have already been characterized and synthesized. The lactotrophs are at least under the partial inhibitory control of the monoamine, dopamine. There are a number of characterized prolactin-releasing factors (PRFs) which include oxytocin, vasoactive intestinal polypeptide, peptide histadine isoleucine, neurotensin, angiotensin II, and possibility substance P. At least two additional peptidic factors remain to be characterized, namely FSH-RF and peptidic prolactin (PRL) release inhibiting factor (PIF). It is the purpose of this grant to further evaluate the role of brain peptides, pituitary hormones, monokines and thymic peptides in the control of gonadotropin and PRL release by direct action on the gland and also to evaluate the role of brain peptides in the control of the release of the releasing and inhibiting hormones themselves. The studies can be divided into the following three principal areas: (1) role of peptides either alone or in combination with other modulating or releasing or inhibiting compounds in control of release of FSH, LH and PRL by direct action on the gland; (2) role of releasing and inhibiting hormones and pituitary hormones in modulating their own release and that of other releasing hormones from the hypothalamus; and (3) the role of peptides in controlling release of the releasing and inhibiting hormones.